This is not a white lasagna, you make a tomato sauce to go with it. But it doesn't have meat in the sauce. I've listed mushrooms as optional....it wasn't in the original recipe, but I like to add them to my sauce.
Saute the onion, garlic, and mushrooms (if using) in olive oil in a large skillet until tender. Add the tomatoes and next 4 ingredients; stir well. Bring to a boil; reduce the heat and simmer, uncovered, for 20 minutes. Remove and discard the bay leaf. Set the sauce aside.
Meanwhile, cook the lasagna noodles according to the package directions. Drain well, and set aside.
Combine the ricotta cheese, spinach, 1/4 cup Parmesan cheese, egg, salt, and pepper; stir well and set aside.
Grease a 13x9x2 inch baking dish. spread 1 1/3 cups of the tomato sauce into the dish. Layer one third of the lasagna noodles, 1/2 of the spinach mixture, 1 cup mozzarella cheese, and 1/4 cup Parmesan cheese in the order listed. Top with 1 1/3 cups of tomato mixture, one third of the lasagna noodles, and the remaining half of the spinach mixture. top with the remaining one third lasagna noodles, 1 1/3 cups tomato mixture, 1/4 cup Parmesan cheese, and 1 cup mozzarella.